Spectroscopic Studies of Cutaneous Photosensitizing Agents–iii. Spin Trapping of Photolysis Products From Sulfanilamide Analogs

The photodecomposition of sulfanilamide (4‐aminobenzenesulfonamide), sulfacetamide. sulfathiazole. sulfadiazine, carbutamide and tolbutamide has been studied using the spin traps 2‐methyl‐2‐nitrosopropanc and 5,5‐dimethyl‐l‐pyrroline‐l‐oxide. The following radicals were trapped during the photolysis of sulfanilamide in aqueous solution: H' and HNC6H4SO2NH, (α‐fission). SO2NH2 and C6H4NH2 (δ fission). H2NC6H4SO2 and NH2 (δ‐fission). Although the C.,H4SO2NH2 and the SO; radicals were also detected these were not formed directly by homolytic bond fission. Homolytic bond fission was also observed during the irradiation of sulfacetamide (α.δ), sulfadiazine (α). carbutamide (α,δ) and tolbutamide (δ). All of the analogs, with the exception of tolbutamide, generated the SO; radical. Sulfacetamide, sulfadiazine and carbutamide generated the C6H4SO2;NHR radical by some process that did not involve homolytic bond fission. The free radicals generated by these agents may play an important role in their phototoxic and photoallergic effects.